diff --git a/pgfw/extension.py b/pgfw/extension.py
index 903bcb7..7a64943 100644
--- a/pgfw/extension.py
+++ b/pgfw/extension.py
@@ -116,6 +116,9 @@ def mirrored(iterable, full=False, tail=True):
             yield item
 
 def get_distance(p0, p1):
+    """
+    Return the distance between two points
+    """
     return sqrt((p0[0] - p1[0]) ** 2 + (p0[1] - p1[1]) ** 2)
 
 def place_in_rect(rect, incoming, contain=True, *args):